Early this morning, police released pictures from surveillance footage showing Roof, 21, as well as the car he was driving.
Debbie Dills, a bookkeeper who works at a florist shop in Kings Mountain, North Carolina, was leaving church in her car when she looked over and saw a driver next to her with a bowl haircut, she told ABC News.
Dills said she then thought there was something about the car that she had heard about somewhere, but couldn't place it. She then spotted the white tag that was in the police description of the shooting suspect.
The observant good Samaritan called her husband and then 911.
Police in Shelby -- about 13 miles west of Kings Mountain where Dills works and 245 miles north of the Charleston church -- said they were informed at 10:32 a.m. today "that a business had contacted them of a possible sighting of the suspect from the Charleston, South Carolina, church shooting traveling into Shelby."
At 10:44 a.m., Roof was apprehended at a traffic stop in Shelby. He was taken into custody five minutes later, police said.
Roof cooperated with the officer who stopped him, according to police.
"I am so pleased we were able to resolve this case quickly," Charleston police Chief Greg Mullen said at a news conference.
A court clerk confirmed to ABC News this afternoon that Roof waived extradition in North Carolina and is cleared to return to South Carolina.